Effect of pH on the Electrochemical Behavior of UNS S31803 Duplex Stainless Steel in H2S-CO2-Cl- Environment

Gao, Chunliang (University of Science and Technology Beijing) | Ding, Jinhui (University of Science and Technology Beijing) | Zhang, Lei (University of Science and Technology Beijing) | Lu, Minxu (University of Science and Technology Beijing) | Li, Dapeng (University of Science and Technology Beijing)



The corrosion behavior of duplex stainless steels (DSS) in H2S-Cl- environment has been discussed for a long time. However, there has been limited work conducted on systematic study of electrochemical corrosion of DSS in H2S-CO2-Cl- environment. In this paper, by using electrochemical impedance spectroscopy (EIS) technique and cyclic potentiodynamic polarization measurements, the electrochemical behavior of UNS S31803 DSS (2205) was investigated in environments containing 60 kPa H2S, 40 kPa CO2 and 150000 mg/L Cl- at 60 °C. The pH in test environments was adjusted to 4.5, 3.5, 3.3 and 3.0 respectively by adding different content of CH3COOH. The EIS results were analyzed by using equivalent circuit and calculating the values of relevant elements. From the cyclic potentiodynamic polarization curves, some important characterization parameters were obtained and analyzed. The effect of solution pH on electrochemical behavior was analyzed. It is indicated that decrease of pH can accelerate corrosion process and make passive film more susceptible to be attacked.